A&P CH. 20 LYMPHATIC SYSTEM & LYMPHOID ORGANS

Name the components of the lymphatic system

A one way network of lymphatic vessels (lymphatics) that collect excess protein containing interstitial fluid

Lymph

Lymph nodes

Lymphatic organs

List the functions of the lymphatic vessels

Return excess fluid to the blood

Return leaked protein to the blood

Carry pathogens to lymph nodes

Carry absorbed fat from the intestines to the blood

Describe the source of lymph?

Interstitial fluid that enters the lymphatic vessels . Originates from blood plasma that leaks out of blood capillaries into the spaces around cells

Which structural modifications are responsible for the increased permeability of lymphatic capillaries?

Mini valves and collagen fibers

What are lymphoid tissues?

specialized parts of the body that provide the structural basis of the immune system by housing phagocytic cells and lymphocytes to prepare for an attack. there are two main types 

diffuse lymphoid tisse

lymphoid follicles (nodules) 

describe diffuse lymphoid tissue

loose arrangement of lymphoid cells and some reticular fibers. they are found everywhere.

describe lymphoid follicles

solid spherical bodies consisting of tightly packed lymphoid cells and reticular fibers (growing center) . they contain germinal centers of proliferating B cells.

Describe the distribution/location of lymphatic capillaries

they weave between tissue cells and blood capillaries and are not found in bone, bone marrow or teeth and are highly limited in the central nervous system. their main function is to collect excess interstitial fluid (which becomes lymph) and begin its transport back toward the bloodstream. lymph transport begins here

Describe how the lymph flows back into the venous system

(Lymphatic capillaries=> Collecting lymphatic vessels=> lymphatic trunks=> lymphatic ducts=> veins)

Lymphatic vessels are low pressure vessels that lack a pump. Describe the mechanisms that ensure lymph transport back into the venous system

• milking action of skeletal muscle fluid

• pressure changes in thorax during breathing

• valves to prevent back flow

• pulsations of nearby arteries

• contractions of smooth muscle in walls of lymphatics

what are primary lymphoid organs

areas where lymphocytes , T and B cells mature (daycare) - red bone marrow and thymus

what are secondary lymphoid organs

areas where mature lymphocytes first encounter their antigen and become activated

Describe the general location, histological structure, and functions of lymph nodes

most are embedded deep in connective tissue but some are nearer to body surface in inguinal, auxiliary and cervical regions.

histologically contain afferent lymphatic vessels, sub scapular sinuses, medullary sinuses, hillum and efferent lymphatic vessels

function to cleanse the lymph and immune system activation. 

Explain why there is a higher number of afferent lymphatic vessels associated with lymph nodes compared to efferent lymphatic vessels

to allow lymphocytes and macrophages time to function

Name the functions of the spleen

filter system for your blood (daycare) 

site of lymphocyte proliferation and immune surveillance  and response 

clenses blood of aged blood cells and platelets

stores broken-down products of rbcs for later use 

stores blood platelets and monocytes for release into blood when needed

may be cute of fetal erythrocyte production

Define MALT and list its major components

mucosa associated lymphoid tissue

found in mucosa of respiratory tract, genitourinary organs, and digestive tract.

largest collections found in ;

tonsils of the entrance of the throat,

Peters patches in the wall of the distal small intestine,

appendix in the large intestines

Describe the function of the thymus

functions as a lymphoid organ where T cells mature. ( no B cells are present here) . most active and latest in size during childhood. gradually gets smaller through adulthood